(1) Field of the Invention
This invention relates to means for sealing the joint between sheet metal ducts having flanged ends that are pressed together by a V-band coupling.
(2) Description of the Prior Art
Sheet metal flange joints mated with V-band type couplings are used frequently in aircraft pneumatic duct systems due to their light weight, simple construction, and ease of installation. This is especially true when the pneumatic system is one in which high temperatures are experienced. For effective coupling with minimum leakage the joints depend upon the faying surfaces of the sheet metal flanges, thereby imposing the requirement that these surfaces be free from scratches and wrinkles, be flat within tolerances such as 0.005 inches, and have a surface roughness in the range of 32 TIR (total indicator reading). Furthermore, the adjoining ducts must be properly aligned, and the tee-bolt on the V-band coupling precisely torqued, to avoid deforming the joint.
If the mating is improper and the permissible leakage rate, typically about 0.01 scfm (standard cubic per minute) per inch of duct diameter, is exceeded the joint must be repaired. The initial installation of the ducts at the aircraft manufacturing facility is usually done with a higher degree of care and in the presence of greater scrutiny than can normally be expected during operational disassembly. As a result, the aircraft purchasers are often subjected to costly duct removal and flange rework procedures when the faying surfaces of mating flanges allow excess gas leakage after operational servicing and the leakage cannot be corrected by burnishing or recontouring of the flange faying surfaces.
Though a variety of sealing devices and techniques are known to those skilled in the relevant art, the applicant is not aware of a seal assembly of the type disclosed particularly suited for direct use with conventional V-band couplings and selectively capable of wide operating temperature ranges.